You assume 8 wins is the floor. With bad QB play 8 wins is not the floor.
The fact that the coaches have routinely put the tamper on talk of Phil going in, even when Book was struggling, shows that they know that 8 wins (or worse) is far more likely than suddenly being a juggernaut. It's crazy to think that the coaching staff would just sit on Trevor Lawrence if he were on the team given how Book earned his job.
If we go 8 wins, the people who are slinging hot takes everywhere will be the first to call for BK's head and will be talking about how stupid it was to bench a guy who had gone 19-3 as a starter going into his 5th year. I'd love to see BK explain why a starter with respect and chemistry with the team, who's now played on the big stage, who's won repeatedly, AND who practices better than QB2 is benched for QB2. BK's answer at this point would have to be "Well, he was ranked higher coming out of high school by Jamie Uyeyama, so we just thought 'YOLO. Dare to be great and all that'"
Also hurting this narrative is that we went for 12 wins last year, and not only that but Book was the reason we went for 12 wins. We went from barely beating Ball State to torching Stanford in a month. So the idea that we can't win 12 with Book is just demonstrably wrong.
It's just such a strawman argument that a football fan saying "I think the guy that the coaches seem to prefer after watching practice a hundred times, who wins like 87% of his games, and who is coming into his 5th year on a statistical uptick is the better guy for the job" is a mediocrity settling wuss.